Canadian patent 808,731 issued Mar. 18, 1969 to Ethicon Inc. discloses a process for the formation of polylactides using a catalyst of the formula R.sub.1 MR.sub.2 wherein R.sub.1 and R.sub.2 are hydrocarbyl groups having from 1 to 12 atoms and M is a divalent metal of group II of the periodic table. The patent teaches that the polymerization may be carried out as a bulk polymerization. However, the patent does not disclose a continuous process. Rather the process is a batch process.
WO 90/01521 (PCT/US89/03380) application in the name of Batelle Memorial Institute discloses a degradable thermoplastic made from lactides. The disclosure teaches at page 19, that the polymerization process may be conducted in a batch, semi-continuous or continuous manner. However, no further details of a continuous process are disclosed and all the examples use a batch process. The disclosure does not suggest a process using a chain of one preferably two or more reactors in series. The Batelle patent application gives an extensive discussion of the prior art and no prior art seems to contemplate a continuous reaction using a chain at least one, preferably two or more reactors in series.
The present seeks to provide a novel process for the continuous polymerization of polylactides in which one, preferably a chain of at least two reactors in series is